Process for the nitrosylation of organic compounds

ABSTRACT

Organic compounds are nitrosylated with nitrous fumes which are essentially free from molecular oxygen, and in which the molar ratio of nitric oxide to nitrogen peroxide is at least 9:1. An advantage of the process is that the product is free from alkali metal salts, so facilitating recovery of the product and re-use of material in the mother liquor. For example, in the production of dinitrosopentamethylenetetramine, by-product formaldehyde can be reconverted into hexamethylenetetramine by adding ammonia, and the mother liquor containing this regenerated hexamethylenetetramine recycled.

United States Patent 91 Conseiller et al.

[ lMarch 20, 1973 [54] PROCESS FOR THE NITROSYLATION OF ORGANICCOMPOUNDS [75] Inventors: Yvon G. M. Conseiller, Paris; .Gerard J.Fontaine, Choisy-Le-Roi,

both of France [73] Assignee: Rhone- Poulene S.A., Paris, France [22]Filed: Sept. 18, 1970 [21] App]. No.: 73,621

[30] Foreign Application Priority Data Sept. 22, 1969 France ..6932160[52] US. Cl ..260/248.5, 260/621 R, 260/268 PH [51] Int. Cl. ..C07d55/52 [58] Field of Search ..260/248.5, 248 RS, 260/621 R, 268 PH, 248.5

[56] References Cited UNITED STATES PATENTS l 1/1960 Johnson et al..260/248 5/1964 Wright et al ..260/248 X OTHER PUBLICATIONS Bell, J.Chromatog, Vol. 24, pp. 253-257 (1966). OD 241 .J5

Hodge .260/248 Primary Examiner-John M. Ford Attorney-Stevens, Davis,Miller & Mosher [5 7] ABSTRACT 'amethylenetetramineby adding ammonia,and the mother liquor containing this regenerated hexamethylenetetraminerecycled.

8 Claims, No Drawings PROCESS FOR THE NITROSYLATION OF ORGANIC COMPOUNDSThis invention relates to a process for the nitrosylation of organiccompounds in the liquid phase by means of nitrous fumes.

The known nitrosylation processes have generally used an alkali metalnitrite in an acid medium (for example sulphuric, acetic, nitric orhydrochloric acid) as the nitrosylating agent. These processes sufferfrom the disadvantage of introducing a rather large amount of alkalimetal salts into the reaction mixture, which has the effect ofcomplicating the recovery of the mother liquors. Furthermore, at the lowtemperatures at which the process is most frequently carried out, nearC., the nitrosylated product can retain a large amount of alkali metalsalt when it precipitates.

A process for the nitrosylation of organic compounds in the liquid phaseby nitrous fumes has now been discovered, which is characterized by thefact that the nitrous fumes do not contain molecular oxygen when theyare introduced into the reaction medium, and that the molar ratio ofnitric oxide to nitrogen peroxide NO/NO is at least 9:1.

Nitrous fumes comprise all gaseous mixtures equivalent to mixtures of NOand N0 with or without molecular oxygen. They can for example beobtained by reduction of nitric acid or of nitrates, by catalyticcombustion of ammonia, or by decomposition of nitrogen sesquioxide.However, the mixtures so obtained generally do not contain nitrogenoxides in the molar ratio required for carrying out the invention, andfor this purpose they must be enriched with nitric odixe, NO. To obtainnitrous fumes practically free from oxygen, it suffices to cool them tobelow 20C. At this temperature the thermodynamic equilibrium issufficiently displaced in favor of the formation of the nitrogenperoxide for practically no molecular oxygen to remain. A mixture ofnitric oxide and oxygen in which the molar ratio of nitric oxide/oxygenis at least 20:1 can, if cooled below 20C., also be used for carryingout the process of the invention. The use of an excess of nitric oxidemakes it possible to avoid the partial formation of dinitrogen pentoxideN 0,, which gives rise to side-reactions such as nitration ordecomposition of the organic reagents. The excess nitric oxide leavingthe reactor is recycled.

It is advantageous to carry out the process at a temperature which isnot too high, i.e. is below 20C. and generally between +l and --5C. andpreferably between 10 and 2C., so as to favor the production of nitrousacid in the reaction medium. Furthermore, it is preferable to ensureintimate contact between the gaseous reagents and the liquid phase byefficient stirring. Gas-recirculating turbine stirrers are particularlysuitable for this purpose.

Examples of the application of the invention are the conversion ofphenol to p-nitroso-phenol, of 1,4- diphenyl-piperazine tol,4-di-p-(nitrosophenyl)- piperazine, and of hexamethylenetetramine todinitrosopentamethylenetetramine. It can however be used innitrosylations generally.

The nitrosylation of hexamethylenetetramine can be represented by thefollowing equation:

In the known processes, the formaldehyde liberated by this reaction isdifficult to recover from the final reaction mixture, which contains alarge amount of alkali metal salt. In the process of the invention theformaldehyde liberated is easily recoverable simply by treating themother liquors, at the end of the reaction, with ammonia, which convertsthe formaldehyde into hexamethylenetetramine. These mother liquors canthen be recycled to subsequent operations.

The actual nitrosylation reaction is in this case advantageously carriedout at a temperature between 2 and 5C. and at a pH of between 7 and 3.

The following example is given by way of illustration.

EXAMPLE 8 kg of waterand 1.4 kg of hexamethylenetetramine (l0 mols) areintroduced into a 30 liter polished stainless steel reactor equippedwith a MORITZ turboabsorber.

The atmospheric gases are flushed from the reactor with nitrogen, themixture is cooled and kept at +5C. by circulating brine, stirring isstarted, the reactor is connected to a nitric oxide gasholder, andnitric oxide is passed through the reactor at the rate of 800 l/hour,with recycling. 4O l/hour of oxygen are simultaneously introduced intothe reactor, and react to form nitrogen peroxide before entering thereaction mixture. The pH of the reaction mixture drops from 6.5 to 3.5after 4 hours under these conditions, and at the end of this time therate of consumption of nitric oxide decreases.

The introduction of oxygen and nitric oxide is stopped, the reactor isflushed with nitrogen and the pH of the mixture is adjusted to 8 byinjecting ammonia whilst keeping the temperature at +5C. The resultingprecipitate is filtered off and twice washed with 500 cm of iced water.After drying the precipitate, 1,335 g ofdinitrosopentamethylenetetramine are obtained (yield 71.7 percent on thehexamethylenetetramine introduced).

The filtrate containing the hexamethylenetetramine regenerated byreaction of ammonia with the byproduct formaldehyde is recycled to asubsequent operation, with 1.03 kg of further hexamethylenetetramine andsufficient'water to make up to 8 kg of water. 1,487 g ofdinitrosopentamethylenetetramine are thus obtained (yield 77.9

percent on the total hexamethylenetetramine, both freshly introduced andregenerated from the first operation).

The operation is restarted a further eight times as above, in each casewith the unreacted and re-formed hexamethylenetetramine being recycled.

The details of the operations are summarized in the table HMT recycled,HMT Formaldeunconverted and efiectively Dry DN PT hyde regenerated,introduced isolated formed,

(calculated) Mols Grams Mols Grains (calculated) 1st operation 10 1, 4007. 17 1,335 7. 17

1st, recycling 2. 65 7. 35 1, 030 7. 99 l, 487 7. 99

2nd recycling. 3. 84 6. 68 935 7. 79 1, 460 7. 79 3rd recycling" 3. 6. 5910 7. 33 l, 364 7. 33

4th recycling-.. 3. 89 6. 1 855 5. 91 1, 100 5. 91

- 5th recycling. 5.07 4. 93 690 7. 95 1, 480 7. 95

6th recycling 3. 37 6. 64 930 7. 09 1, 320 7. 09

7th recycling 4. U9 5. 90 825 7. 31 1, 360 7. 31

8th recycling 3. 91 6. 10 855 6. 64 1, 235 6. 64

9th recycling. 4. 46 6. 52 773 5. 80 1,080 5. 80

NOTE.I11 this table, hexamethylenetetramine has been abbreviated to HMTand nitrosopentamethylenetetramine to DNPT.

We claim:

1. Process for the nitrosylation of phenol, 1,4- diphenyl-piperazine orhexamethylenetetramine in the liquid phase by nitrous fumes which aresubstantially free from molecular oxygen when they are introduced intothe reaction mixture, and where the molar ratio NO/NO in the nitrousfumes is at least 9:1.

2. Process according to claim 1, inwhich the nitrous fumes areintroduced into the reaction zone at a temperature below 20C.

3. Process according to claim 1', in which the nitrosylation-is effectedat a temperature of +l 5 to 5C..

4. Process according to claim 3, in which the temperature is +l0 to +2C.

5. Process according to claim 1, inwhich the nitrous fumes used areobtained by mixing oxygen with at least 50 molar equivalents of nitricoxide at a temperature. below 20C., or by mixing the oxygen and nitricoxide

2. Process according to claim 1, in which the nitrous fumes areintroduced into the reaction zone at a temperature below 20*C. 3.Process according to claim 1, in which the nitrosylation is effected ata temperature of +15* to - 5*C.
 4. Process according to claim 3, inwhich the temperature is +10* to +2*C.
 5. Process according to claim 1,in which the nitrous fumes used are obtained by mixing oxygen with atleast 20 molar equivalents of nitric oxide at a temperature below 20*C.,or by mixing the oxygen and nitric oxide at a temperature above 20*C.and cooling the mixture to a temperature below 20*C.
 6. Processaccording to claim 1, in which dinitrosopentamethylenetetramine isformed by the nitrosylation of hexamethylenetetramine.
 7. Processaccording to claim 6, in which the reaction is effected at a temperatureof 2* to 5*C.
 8. Process according to claim 6, in which the precipitateof dinitrosopentamethylenetetramine formed is separated from thereaction mixture, ammonia is added to the mother liquor to regeneratehexamethylenetetramine from by-product formaldehyde, and the regeneratedhexamethylenetetramine is recycled.